Applications of electro-optic displays

ABSTRACT

Electro-optic, especially electrophoretic, displays are used in variety of architectural and furniture applications, including a tile (100) comprising an electro-optic layer (110) capable of changing the color of the file, front and multiple rear electrodes and a light-transmissive polymeric layer (102), the exposed surface of which is textured to provide a plurality of facets inclined to the plane of the tile (100), the rear electrodes being aligned with the facets. A variable color writable board is also provided.

REFERENCE TO RELATED APPLICATIONS

This application claims benefit of provisional Application Ser. No.62/077,154, filed Nov. 7, 2014 and of provisional Application Ser. No.62/099,732, filed Jan. 5, 2015. The entire contents this applicationsand of all U.S. patents and published and copending applicationsmentioned below, are herein incorporated by reference.

BACKGROUND OF INVENTION

This invention relates to applications of electro-optic displays. Morespecifically, this invention relates to uses of electro-optic displays,especially but not exclusively, particle-based electrophoretic displays,in architectural, furnishing and similar applications.

The term “electro-optic”, as applied to a material or a display, is usedherein in its conventional meaning in the imaging art to refer to amaterial having first and second display states differing in at leastone optical property, the material being changed from its first to itssecond display state by application of an electric field to thematerial. Although the optical property is typically color perceptibleto the human eye, it may be another optical property, such as opticaltransmission, reflectance, luminescence or, in the case of displaysintended for machine reading, pseudo-color in the sense of a change inreflectance of electromagnetic wavelengths outside the visible range.

The term “gray state” is used herein in its conventional meaning in theimaging art to refer to a state intermediate two extreme optical statesof a pixel, and does not necessarily imply a black-white transitionbetween these two extreme states. For example, several of the E Inkpatents and published applications referred to below describeelectrophoretic displays in which the extreme states are white and deepblue, so that an intermediate “gray state” would actually be pale blue.Indeed, as already mentioned, the change in optical state may not be acolor change at all. The terms “black” and “white” may be usedhereinafter to refer to the two extreme optical states of a display, andshould be understood as normally including extreme optical states whichare not strictly black and white, for example the aforementioned whiteand dark blue states. The term “monochrome” may be used hereinafter todenote a drive scheme which only drives pixels to their two extremeoptical states with no intervening gray states.

Some electro-optic materials are solid in the sense that the materialshave solid external surfaces, although the materials may, and often do,have internal liquid- or gas-filled spaces. Such displays using solidelectro-optic materials may hereinafter for convenience be referred toas “solid electro-optic displays”. Thus, the term “solid electro-opticdisplays” includes rotating bichromal member displays, encapsulatedelectrophoretic displays, microcell electrophoretic displays andencapsulated liquid crystal displays.

The terms “bistable” and “bistability” are used herein in theirconventional meaning in the art to refer to displays comprising displayelements having first and second display states differing in at leastone optical property, and such that after any given element has beendriven, by means of an addressing pulse of finite duration, to assumeeither its first or second display state, after the addressing pulse hasterminated, that state will persist for at least several times, forexample at least four times, the minimum duration of the addressingpulse required to change the state of the display element. It is shownin U.S. Pat. No. 7,170,670 that some particle-based electrophoreticdisplays capable of gray scale are stable not only in their extremeblack and white states but also in their intermediate gray states, andthe same is true of some other types of electro-optic displays. Thistype of display is properly called “multi-stable” rather than bistable,although for convenience the term “bistable” may be used herein to coverboth bistable and multi-stable displays.

Several types of electro-optic displays are known. One type ofelectro-optic display is a rotating bichromal member type as described,for example, in U.S. Pat. Nos. 5,808,783; 5,777,782; 5,760,761;6,054,071 6,055,091; 6,097,531; 6,128,124; 6,137,467; and 6,147,791(although this type of display is often referred to as a “rotatingbichromal ball” display, the term “rotating bichromal member” ispreferred as more accurate since in some of the patents mentioned abovethe rotating members are not spherical). Such a display uses a largenumber of small bodies (typically spherical or cylindrical) which havetwo or more sections with differing optical characteristics, and aninternal dipole. These bodies are suspended within liquid-filledvacuoles within a matrix, the vacuoles being filled with liquid so thatthe bodies are free to rotate. The appearance of the display is changedby applying an electric field thereto, thus rotating the bodies tovarious positions and varying which of the sections of the bodies isseen through a viewing surface. This type of electro-optic medium istypically bistable.

Another type of electro-optic display uses an electrochromic medium, forexample an electrochromic medium in the form of a nanochromic filmcomprising an electrode formed at least in part from a semi-conductingmetal oxide and a plurality of dye molecules capable of reversible colorchange attached to the electrode; see, for example O'Regan, B., et al.,Nature 1991, 353, 737; and Wood, D., Information Display, 18(3), 24(March 2002). See also Bach, U., et al., Adv. Mater., 2002, 14(11), 845.Nanochromic films of this type are also described, for example, in U.S.Pat. Nos. 6,301,038; 6,870,657; and 6,950,220. This type of medium isalso typically bistable.

Another type of electro-optic display is an electro-wetting displaydeveloped by Philips and described in Hayes, R. A., et al., “Video-SpeedElectronic Paper Based on Electrowetting”, Nature, 425, 383-385 (2003).It is shown in U.S. Pat. No. 7,420,549 that such electro-wettingdisplays can be made bistable.

One type of electro-optic display, which has been the subject of intenseresearch and development for a number of years, is the particle-basedelectrophoretic display, in which a plurality of charged particles movethrough a fluid under the influence of an electric field.Electrophoretic displays can have attributes of good brightness andcontrast, wide viewing angles, state bistability, and low powerconsumption when compared with liquid crystal displays. Nevertheless,problems with the long-term image quality of these displays haveprevented their widespread usage. For example, particles that make upelectrophoretic displays tend to settle, resulting in inadequateservice-life for these displays.

As noted above, electrophoretic media require the presence of a fluid.In most prior art electrophoretic media, this fluid is a liquid, butelectrophoretic media can be produced using gaseous fluids; see, forexample, Kitamura, T., et al., “Electrical toner movement for electronicpaper-like display”, IDW Japan, 2001, Paper HCS1-1, and Yamaguchi, Y.,et al., “Toner display using insulative particles chargedtriboelectrically”, IDW Japan, 2001, Paper AMD4-4). See also U.S. Pat.Nos. 7,321,459 and 7,236,291. Such gas-based electrophoretic mediaappear to be susceptible to the same types of problems due to particlesettling as liquid-based electrophoretic media, when the media are usedin an orientation which permits such settling, for example in a signwhere the medium is disposed in a vertical plane. Indeed, particlesettling appears to be a more serious problem in gas-basedelectrophoretic media than in liquid-based ones, since the lowerviscosity of gaseous suspending fluids as compared with liquid onesallows more rapid settling of the electrophoretic particles.

Numerous patents and applications assigned to or in the names of theMassachusetts Institute of Technology (MIT) and E Ink Corporationdescribe various technologies used in encapsulated electrophoretic andother electro-optic media. Such encapsulated media comprise numeroussmall capsules, each of which itself comprises an internal phasecontaining electrophoretically-mobile particles in a fluid medium, and acapsule wall surrounding the internal phase. Typically, the capsules arethemselves held within a polymeric binder to form a coherent layerpositioned between two electrodes. The technologies described in thesepatents and applications include:

-   -   (a) Electrophoretic particles, fluids and fluid additives; see        for example U.S. Pat. Nos. 5,961,804; 6,017,584; 6,120,588;        6,120,839; 6,262,706; 6,262,833; 6,300,932; 6,323,989;        6,377,387; 6,515,649; 6,538,801; 6,580,545; 6,652,075;        6,693,620; 6,721,083; 6,727,881; 6,822,782; 6,870,661;        7,002,728; 7,038,655; 7,170,670; 7,180,649; 7,230,750;        7,230,751; 7,236,290; 7,247,379; 7,312,916; 7,375,875;        7,411,720; 7,532,388; 7,679,814; 7,746,544; 7,848,006;        7,903,319; 8,018,640; 8,115,729; 8,199,395; 8,270,064;        8,305,341; 8,390,918; 8,582,196; 8,593,718; and 8,654,436; and        U.S. Patent Applications Publication Nos. 2005/0012980;        2009/0009852; 2009/0206499; 2009/0225398; 2010/0148385;        2014/0078857; 2014/0211296; 2014/0347718; 2015/0015932;        2015/0177589; and 2015/0218384;    -   (b) Capsules, binders and encapsulation processes; see for        example U.S. Pat. Nos. 5,930,026; 6,067,185; 6,130,774;        6,172,798; 6,249,271; 6,327,072; 6,392,785; 6,392,786;        6,459,418; 6,839,158; 6,866,760; 6,922,276; 6,958,848;        6,987,603; 7,061,663; 7,071,913; 7,079,305; 7,109,968;        7,110,164; 7,202,991; 7,242,513; 7,304,634; 7,339,715;        7,391,555; 7,411,719; 7,477,444; 7,561,324; 7,848,007;        7,910,175; 7,952,790; 8,035,886; 8,129,655; 8,446,664; and        9,005,494; and U.S. Patent Applications Publication Nos.        2005/0156340; 2007/0091417; 2008/0130092; 2009/0122389; and        2011/0286081;    -   (c) Films and sub-assemblies containing electro-optic materials;        see for example U.S. Pat. Nos. 6,825,829; 6,982,178; 7,236,292;        7,443,571; 7,513,813; 7,561,324; 7,636,191; 7,649,666;        7,728,811; 7,729,039; 7,791,782; 7,839,564; 7,843,621;        7,843,624; 8,034,209; 8,068,272; 8,077,381; 8,177,942;        8,390,301; 8,482,852; 8,786,929; 8,830,553; 8,854,721; and        9,075,280; and U.S. Patent Applications Publication Nos.        2009/0109519; 2009/0168067; 2011/0164301; 2014/0027044;        2014/0115884; and 2014/0340738;    -   (d) Backplanes, adhesive layers and other auxiliary layers and        methods used in displays; see for example U.S. Pat. No.        D485,294; 6,124,851; 6,130,773; 6,177,921; 6,232,950; 6,252,564;        6,312,304; 6,312,971; 6,376,828; 6,392,786; 6,413,790;        6,422,687; 6,445,374; 6,480,182; 6,498,114; 6,506,438;        6,518,949; 6,521,489; 6,535,197; 6,545,291; 6,639,578;        6,657,772; 6,664,944; 6,680,725; 6,683,333; 6,724,519;        6,750,473; 6,816,147; 6,819,471; 6,825,068; 6,831,769;        6,842,167; 6,842,279; 6,842,657; 6,865,010; 6,967,640;        6,980,196; 7,012,735; 7,030,412; 7,075,703; 7,106,296;        7,110,163; 7,116,318; 7,148,128; 7,167,155; 7,173,752;        7,176,880; 7,190,008; 7,206,119; 7,223,672; 7,230,751;        7,256,766; 7,259,744; 7,280,094; 7,327,511; 7,349,148;        7,352,353; 7,365,394; 7,365,733; 7,382,363; 7,388,572;        7,442,587; 7,492,497; 7,535,624; 7,551,346; 7,554,712;        7,583,427; 7,598,173; 7,605,799; 7,636,191; 7,649,674;        7,667,886; 7,672,040; 7,688,497; 7,733,335; 7,785,988;        7,843,626; 7,859,637; 7,893,435; 7,898,717; 7,957,053;        7,986,450; 8,009,344; 8,027,081; 8,049,947; 8,077,141;        8,089,453; 8,208,193; 8,373,211; 8,389,381; 8,498,042;        8,610,988; 8,728,266; 8,754,859; 8,830,560; 8,891,155;        8,989,886; 9,152,003; and 9,152,004; and U.S. Patent        Applications Publication Nos. 2002/0060321; 2004/0105036;        2005/0122306; 2005/0122563; 2007/0052757; 2007/0097489;        2007/0109219; 2009/0122389; 2009/0315044; 2011/0026101;        2011/0140744; 2011/0187683; 2011/0187689; 2011/0292319;        2013/0278900; 2014/0078024; 2014/0139501; 2014/0300837;        2015/0171112; 2015/0205178; 2015/0226986; 2015/0227018;        2015/0228666; and 2015/0261057; and International Application        Publication No. WO 00/38000; European Patents Nos. 1,099,207 B1        and 1,145,072 B1;    -   (e) Color formation and color adjustment; see for example U.S.        Pat. Nos. 6,017,584; 6,664,944; 6,864,875; 7,075,502; 7,167,155;        7,667,684; 7,791,789; 7,839,564; 7,956,841; 8,040,594;        8,054,526; 8,098,418; 8,213,076; 8,363,299; 8,441,714;        8,441,716; 8,466,852; 8,576,470; 8,576,475; 8,593,721;        8,797,634; 8,830,559; 8,873,129; and 8,902,153; and U.S. Patent        Applications Publication Nos. 2007/0223079; 2008/0023332;        2008/0043318; 2008/0048970; 2009/0004442; 2009/0225398;        2010/0103502; 2010/0156780; 2011/0164307; 2012/0182597;        2012/0326957; 2013/0141778; 2013/0242378; 2013/0258449;        2013/0278995; 2014/0055841; 2014/0226198; 2014/0240817;        2014/0340430; 2014/0362213; 2015/0118390; and 2015/0124345;    -   (f) Methods for driving displays; see for example U.S. Pat. Nos.        5,930,026; 6,445,489; 6,504,524; 6,512,354; 6,531,997;        6,753,999; 6,825,970; 6,900,851; 6,995,550; 7,012,600;        7,023,420; 7,034,783; 7,116,466; 7,119,772; 7,193,625;        7,202,847; 7,259,744; 7,304,787; 7,312,794; 7,327,511;        7,453,445; 7,492,339; 7,528,822; 7,545,358; 7,583,251;        7,602,374; 7,612,760; 7,679,599; 7,688,297; 7,729,039;        7,733,311; 7,733,335; 7,787,169; 7,952,557; 7,956,841;        7,999,787; 8,077,141; 8,125,501; 8,139,050; 8,174,490;        8,289,250; 8,300,006; 8,305,341; 8,314,784; 8,373,649;        8,384,658; 8,558,783; 8,558,785; 8,593,396; and 8,928,562; and        U.S. Patent Applications Publication Nos. 2003/0102858;        2005/0253777; 2007/0091418; 2007/0103427; 2008/0024429;        2008/0024482; 2008/0136774; 2008/0291129; 2009/0174651;        2009/0179923; 2009/0195568; 2009/0322721; 2010/0220121;        2010/0265561; 2011/0193840; 2011/0193841; 2011/0199671;        2011/0285754; 2013/0063333; 2013/0194250; 2013/0321278;        2014/0009817; 2014/0085350; 2014/0240373; 2014/0253425;        2014/0292830; 2014/0333685; 2015/0070744; 2015/0109283;        2015/0213765; 2015/0221257; and 2015/0262255;    -   (g) Applications of displays; see for example U.S. Pat. Nos.        6,118,426; 6,473,072; 6,704,133; 6,710,540; 6,738,050;        6,825,829; 7,030,854; 7,119,759; 7,312,784; and U.S. Pat. Nos.        8,009,348; 7,705,824; 8,064,962; and 8,553,012; and U.S. Patent        Applications Publication Nos. 2002/0090980; 2004/0119681; and        2007/0285385; and International Application Publication No. WO        00/36560; and    -   (h) Non-electrophoretic displays, as described in U.S. Pat. Nos.        6,241,921; 6,950,220; 7,420,549 8,319,759; and 8,994,705 and        U.S. Patent Application Publication No. 2012/0293858.

Many of the aforementioned patents and applications recognize that thewalls surrounding the discrete microcapsules in an encapsulatedelectrophoretic medium could be replaced by a continuous phase, thusproducing a so-called polymer-dispersed electrophoretic display, inwhich the electrophoretic medium comprises a plurality of discretedroplets of an electrophoretic fluid and a continuous phase of apolymeric material, and that the discrete droplets of electrophoreticfluid within such a polymer-dispersed electrophoretic display may beregarded as capsules or microcapsules even though no discrete capsulemembrane is associated with each individual droplet; see for example,the aforementioned U.S. Pat. No. 6,866,760. Accordingly, for purposes ofthe present application, such polymer-dispersed electrophoretic mediaare regarded as sub-species of encapsulated electrophoretic media.

A related type of electrophoretic display is a so-called “microcellelectrophoretic display”. In a microcell electrophoretic display, thecharged particles and the fluid are not encapsulated withinmicrocapsules but instead are retained within a plurality of cavitiesformed within a carrier medium, typically a polymeric film. See, forexample, U.S. Pat. Nos. 6,672,921 and 6,788,449, both assigned to SipixImaging, Inc.

Although electrophoretic media are often opaque (since, for example, inmany electrophoretic media, the particles substantially blocktransmission of visible light through the display) and operate in areflective mode, many electrophoretic displays can be made to operate ina so-called “shutter mode” in which one display state is substantiallyopaque and one is light-transmissive. See, for example, U.S. Pat. Nos.5,872,552; 6,130,774; 6,144,361; 6,172,798; 6,271,823; 6,225,971; and6,184,856. Dielectrophoretic displays, which are similar toelectrophoretic displays but rely upon variations in electric fieldstrength, can operate in a similar mode; see U.S. Pat. No. 4,418,346.Other types of electro-optic displays may also be capable of operatingin shutter mode. Electro-optic media operating in shutter mode may beuseful in multi-layer structures for full color displays; in suchstructures, at least one layer adjacent the viewing surface of thedisplay operates in shutter mode to expose or conceal a second layermore distant from the viewing surface.

An encapsulated electrophoretic display typically does not suffer fromthe clustering and settling failure mode of traditional electrophoreticdevices and provides further advantages, such as the ability to print orcoat the display on a wide variety of flexible and rigid substrates.(Use of the word “printing” is intended to include all forms of printingand coating, including, but without limitation: pre-metered coatingssuch as patch die coating, slot or extrusion coating, slide or cascadecoating, curtain coating; roll coating such as knife over roll coating,forward and reverse roll coating; gravure coating; dip coating; spraycoating; meniscus coating; spin coating; brush coating; air knifecoating; silk screen printing processes; electrostatic printingprocesses; thermal printing processes; ink jet printing processes;electrophoretic deposition (See U.S. Pat. No. 7,339,715); and othersimilar techniques.) Thus, the resulting display can be flexible.Further, because the display medium can be printed (using a variety ofmethods), the display itself can be made inexpensively.

Other types of electro-optic materials may also be used in the presentinvention.

An electro-optic display normally comprises a layer of electro-opticmaterial and at least two other layers disposed on opposed sides of theelectro-optic material, one of these two layers being an electrodelayer. In most such displays both the layers are electrode layers, andone or both of the electrode layers are patterned to define the pixelsof the display. For example, one electrode layer may be patterned intoelongate row electrodes and the other into elongate column electrodesrunning at right angles to the row electrodes, the pixels being definedby the intersections of the row and column electrodes. Alternatively,and more commonly, one electrode layer has the form of a singlecontinuous electrode and the other electrode layer is patterned into amatrix of pixel electrodes, each of which defines one pixel of thedisplay. In another type of electro-optic display, which is intended foruse with a stylus, print head or similar movable electrode separate fromthe display, only one of the layers adjacent the electro-optic layercomprises an electrode, the layer on the opposed side of theelectro-optic layer typically being a protective layer intended toprevent the movable electrode damaging the electro-optic layer.

The manufacture of a three-layer electro-optic display normally involvesat least one lamination operation. For example, in several of theaforementioned MIT and E Ink patents and applications, there isdescribed a process for manufacturing an encapsulated electrophoreticdisplay in which an encapsulated electrophoretic medium comprisingcapsules in a binder is coated on to a flexible substrate comprisingindium-tin-oxide (ITO) or a similar conductive coating (which acts asone electrode of the final display) on a plastic film, thecapsules/binder coating being dried to form a coherent layer of theelectrophoretic medium firmly adhered to the substrate. Separately, abackplane, containing an array of pixel electrodes and an appropriatearrangement of conductors to connect the pixel electrodes to drivecircuitry, is prepared. To form the final display, the substrate havingthe capsule/binder layer thereon is laminated to the backplane using alamination adhesive. (A very similar process can be used to prepare anelectrophoretic display usable with a stylus or similar movableelectrode by replacing the backplane with a simple protective layer,such as a plastic film, over which the stylus or other movable electrodecan slide.) In one preferred form of such a process, the backplane isitself flexible and is prepared by printing the pixel electrodes andconductors on a plastic film or other flexible substrate. The obviouslamination technique for mass production of displays by this process isroll lamination using a lamination adhesive. Similar manufacturingtechniques can be used with other types of electro-optic displays. Forexample, a microcell electrophoretic medium or a rotating bichromalmember medium may be laminated to a backplane in substantially the samemanner as an encapsulated electrophoretic medium.

As discussed in the aforementioned U.S. Pat. No. 6,982,178, (see column3, lines 63 to column 5, line 46) many of the components used in solidelectro-optic displays, and the methods used to manufacture suchdisplays, are derived from technology used in liquid crystal displays(LCD's), which are of course also electro-optic displays, though using aliquid rather than a solid medium. For example, solid electro-opticdisplays may make use of an active matrix backplane comprising an arrayof transistors or diodes and a corresponding array of pixel electrodes,and a “continuous” front electrode (in the sense of an electrode whichextends over multiple pixels and typically the whole display) on atransparent substrate, these components being essentially the same as inLCD's. However, the methods used for assembling LCD's cannot be usedwith solid electro-optic displays. LCD's are normally assembled byforming the backplane and front electrode on separate glass substrates,then adhesively securing these components together leaving a smallaperture between them, placing the resultant assembly under vacuum, andimmersing the assembly in a bath of the liquid crystal, so that theliquid crystal flows through the aperture between the backplane and thefront electrode. Finally, with the liquid crystal in place, the apertureis sealed to provide the final display.

This LCD assembly process cannot readily be transferred to solidelectro-optic displays. Because the electro-optic material is solid, itmust be present between the backplane and the front electrode beforethese two integers are secured to each other. Furthermore, in contrastto a liquid crystal material, which is simply placed between the frontelectrode and the backplane without being attached to either, a solidelectro-optic medium normally needs to be secured to both; in most casesthe solid electro-optic medium is formed on the front electrode, sincethis is generally easier than forming the medium on thecircuitry-containing backplane, and the front electrode/electro-opticmedium combination is then laminated to the backplane, typically bycovering the entire surface of the electro-optic medium with an adhesiveand laminating under heat, pressure and possibly vacuum. Accordingly,most prior art methods for final lamination of solid electrophoreticdisplays are essentially batch methods in which (typically) theelectro-optic medium, a lamination adhesive and a backplane are broughttogether immediately prior to final assembly, and it is desirable toprovide methods better adapted for mass production.

Electro-optic displays are often costly; for example, the cost of thecolor LCD found in a portable computer is typically a substantialfraction of the entire cost of the computer. As the use of electro-opticdisplays spreads to devices, such as cellular telephones and personaldigital assistants (PDA's), much less costly than portable computers,there is great pressure to reduce the costs of such displays. Theability to form layers of some solid electro-optic media by printingtechniques on flexible substrates, as discussed above, opens up thepossibility of reducing the cost of electro-optic components of displaysby using mass production techniques such as roll-to-roll coating usingcommercial equipment used for the production of coated papers, polymericfilms and similar media.

The aforementioned U.S. Pat. No. 6,982,178 describes a method ofassembling a solid electro-optic display (including an encapsulatedelectrophoretic display) which is well adapted for mass production.Essentially, this patent describes a so-called “front plane laminate”(“FPL”) which comprises, in order, a light-transmissiveelectrically-conductive layer; a layer of a solid electro-optic mediumin electrical contact with the electrically-conductive layer; anadhesive layer; and a release sheet. Typically, the light-transmissiveelectrically-conductive layer will be carried on a light-transmissivesubstrate, which is preferably flexible, in the sense that the substratecan be manually wrapped around a drum (say) 10 inches (254 mm) indiameter without permanent deformation. The term “light-transmissive” isused in this patent and herein to mean that the layer thus designatedtransmits sufficient light to enable an observer, looking through thatlayer, to observe the change in display states of the electro-opticmedium, which will normally be viewed through theelectrically-conductive layer and adjacent substrate (if present); incases where the electro-optic medium displays a change in reflectivityat non-visible wavelengths, the term “light-transmissive” should ofcourse be interpreted to refer to transmission of the relevantnon-visible wavelengths. The substrate will typically be a polymericfilm, and will normally have a thickness in the range of about 1 toabout 25 mil (25 to 634 μm), preferably about 2 to about 10 mil (51 to254 μm). The electrically-conductive layer is conveniently a thin metalor metal oxide layer of, for example, aluminum or ITO, or may be aconductive polymer. Poly(ethylene terephthalate) (PET) films coated withaluminum or ITO are available commercially, for example as “aluminizedMylar” (“Mylar” is a Registered Trade Mark) from E.I. du Pont de Nemours& Company, Wilmington Del., and such commercial materials may be usedwith good results in the front plane laminate.

The aforementioned U.S. Pat. No. 6,982,178 also describes a method fortesting the electro-optic medium in a front plane laminate prior toincorporation of the front plane laminate into a display. In thistesting method, the release sheet is provided with an electricallyconductive layer, and a voltage sufficient to change the optical stateof the electro-optic medium is applied between this electricallyconductive layer and the electrically conductive layer on the opposedside of the electro-optic medium. Observation of the electro-opticmedium will then reveal any faults in the medium, thus avoidinglaminating faulty electro-optic medium into a display, with theresultant cost of scrapping the entire display, not merely the faultyfront plane laminate.

The aforementioned U.S. Pat. No. 6,982,178 also describes a secondmethod for testing the electro-optic medium in a front plane laminate byplacing an electrostatic charge on the release sheet, thus forming animage on the electro-optic medium. This image is then observed in thesame way as before to detect any faults in the electro-optic medium.

Assembly of an electro-optic display using such a front plane laminatemay be effected by removing the release sheet from the front planelaminate and contacting the adhesive layer with the backplane underconditions effective to cause the adhesive layer to adhere to thebackplane, thereby securing the adhesive layer, layer of electro-opticmedium and electrically-conductive layer to the backplane. This processis well-adapted to mass production since the front plane laminate may bemass produced, typically using roll-to-roll coating techniques, and thencut into pieces of any size needed for use with specific backplanes.

U.S. Pat. No. 7,561,324 describes a so-called “double release sheet”which is essentially a simplified version of the front plane laminate ofthe aforementioned U.S. Pat. No. 6,982,178. One form of the doublerelease sheet comprises a layer of a solid electro-optic mediumsandwiched between two adhesive layers, one or both of the adhesivelayers being covered by a release sheet. Another form of the doublerelease sheet comprises a layer of a solid electro-optic mediumsandwiched between two release sheets. Both forms of the double releasefilm are intended for use in a process generally similar to the processfor assembling an electro-optic display from a front plane laminatealready described, but involving two separate laminations; typically, ina first lamination the double release sheet is laminated to a frontelectrode to form a front sub-assembly, and then in a second laminationthe front sub-assembly is laminated to a backplane to form the finaldisplay, although the order of these two laminations could be reversedif desired.

U.S. Pat. No. 7,839,564 describes a so-called “inverted front planelaminate”, which is a variant of the front plane laminate described inthe aforementioned U.S. Pat. No. 6,982,178. This inverted front planelaminate comprises, in order, at least one of a light-transmissiveprotective layer and a light-transmissive electrically-conductive layer;an adhesive layer; a layer of a solid electro-optic medium; and arelease sheet. This inverted front plane laminate is used to form anelectro-optic display having a layer of lamination adhesive between theelectro-optic layer and the front electrode or front substrate; asecond, typically thin layer of adhesive may or may not be presentbetween the electro-optic layer and a backplane. Such electro-opticdisplays can combine good resolution with good low temperatureperformance.

Light modulators represent a potentially important market forelectro-optic media. As the energy performance of buildings and vehiclesbecomes increasingly important, electro-optic media can be used ascoatings on windows (including skylights and sunroofs) to enable theproportion of incident radiation transmitted through the windows to beelectronically controlled by varying the optical state of theelectro-optic media. Effective implementation of such“variable-transmissivity” (“VT”) technology in buildings is expected toprovide (1) reduction of unwanted heating effects during hot weather,thus reducing the amount of energy needed for cooling, the size of airconditioning plants, and peak electricity demand; (2) increased use ofnatural daylight, thus reducing energy used for lighting and peakelectricity demand; and (3) increased occupant comfort by increasingboth thermal and visual comfort. Even greater benefits would be expectedto accrue in an automobile, where the ratio of glazed surface toenclosed volume is significantly larger than in a typical building.Specifically, effective implementation of VT technology in automobilesis expected to provide not only the aforementioned benefits but also (1)increased motoring safety, (2) reduced glare, (3) enhanced mirrorperformance (by using an electro-optic coating on the mirror), and (4)increased ability to use heads-up displays. Other potential applicationsof VT technology include privacy glass and glare-guards in electronicdevices.

Electrophoretic and similar bistable electro-optic display media haveuntil now been primarily used in electronic document readers (E-bookreaders), with some use in electronic storage media such as flashdrives, portable computers, tablet computers, cellular telephones, smartcards, signs, watches, shelf labels, and variable transmission windows.However, the low power requirements, flexibility and light weight ofelectrophoretic and similar bistable electro-optic display media renderthem useful in numerous other applications, especially architectural,furniture and related applications.

SUMMARY OF INVENTION

In one aspect, this invention provides a tile comprising, in order, alight-transmissive front layer, at least one front electrode, anelectro-optic layer capable of changing the color of the tile, and aplurality of rear electrodes, the exposed surface of the front layerbeing textured to provide a plurality of facets having a plurality ofinclinations to the plane of the tile, and the plurality of rearelectrodes providing at least one electrode located within each facet ofthe front layer.

These tiles of the present invention may be used as wall, ceiling orother tiles, or may be used in screens, dividers or similar devices.Alternatively, the tiles may be mounted on or within the surfaces offurniture and architectural fittings, including table tops, chairs,countertops, door and cabinets.

In the tile of the present invention, at least some (i.e., one or more),and preferably a majority, of the facets do not lie parallel to theplane of the electro-optic layer and of the tile itself “Inclining” somefacets in this manner assists in the production of interesting visualeffects, and also reduces the effects of any mis-alignment between thefacets themselves and the rear electrodes. The individual facetsthemselves need not be strictly planar; they may be flat, or convex orconcave outwards. Indeed, interesting visual effects can be produced bymaking the facets slightly concave outwards; especially under highpowered lights, such concave facets can provide an illusion of atriplanar display, with the facets providing one image in front of theactual surface of the display and one apparently behind the display, inaddition to the actual display surface. Similarly, we do not exclude thepossibility that the transitions between adjacent facets might be in theform of curved areas rather than sharp edges.

As illustrated in the drawings and discussed below, the facets desirablyvary in both size and shape, but desirably a majority of the facets arein the form of polygons, preferably irregular polygons, having from fourto eight vertices. While the invention is primarily described below withreference to electro-optic media having only two colors, electro-opticmedia having more colors may be used; in particular, three and fourcolor media capable of displaying black, white and one or two othercolors (typically one or both of red and yellow) are known and mayusefully be employed in the present tiles.

In the tile of the present invention, the plurality of rear electrodesprovides at least one electrode located within each of the facets of thefront layer. In one form of the tile, the rear electrodes may be ofsubstantially the same size and shape as the facets of the front layer.Such an arrangement may be provided by having the backplane in the formof a printed circuit board having the electrodes mounted thereon;alternatively, a screen printed backplane could be used. However, it isnot essential that there be only a single electrode behind each facet.For example, an active matrix backplane may be used, with the electrodesarranged in the usual matrix of rows and columns. Such an active matrixbackplane may be used to create interesting optical effects incombination with the faceted front layer. Alternatively such an activematrix backplane may be driven so that all the electrodes lying within asingle facet of the front layer are maintained at the same potential sothat all these electrodes essentially form a single “virtual electrode”having the shape of the single facet. In commercial production, use ofsuch an active matrix backplane, together with a controller capable ofdefining any desired pattern of virtual electrodes corresponding to anydesired pattern of facets on the front layer, may be more economicalthan producing a plurality of types of backplanes each having a set ofelectrodes corresponding to the facet pattern on one type of frontlayer.

There are other ways in which more than one pixel electrode might beprovided behind a single facet. In particular, if (as is commonly thecase), individual tiles are square or rectangular, it may beadvantageous to arrange the facets so that a facet on the edge of onetile aligns with a facet on the adjacent edge of the next tile, so thatthe two facets on adjacent tiles in effect form a single “compound”facet. To this end, the arrangement of the facets may be such that, whenthe tile is surrounded by other tiles having the same facet pattern, atleast some of the lines dividing adjacent facets continue unbrokenacross the joins between adjacent tiles. Although of course thiscompound facet will be adjacent two separate pixel electrodes on the twoseparate tiles, it is advantageous to arrange the driving of the tilesso that these two pixel electrodes always remain at the same potentialrelative to their respective common electrodes, so that the two parts ofthe compound facet appear as a single facet, thus visually “breaking up”the straight line between the adjacent tiles and (when repeated over theedges between numerous adjacent tiles) giving the impression of acontinuous sheet of color-changing paneling rather than an assembly ofdiscrete tiles. Similarly, it is advantageous for the four facets in thecorners of a rectangular tile to be arranged to as to form a singlecompound facet.

The electro-optic medium may be laminated directly on to the backplane.

As already indicated, in another aspect, this invention provides a wall,ceiling, floor, piece of furniture or architectural surface (all ofwhich will hereinafter for convenience be referred to as “architecturalsurfaces”) having fixed thereto or embedded therein an electro-opticlayer capable of changing the color of the architectural surface. Oneform of such a variable color architectural surface comprises a tile(which may be a wall, ceiling or other tile) which may be used as adirect replacement for a conventional tile. Such a tile may comprise alight-transmissive (preferably essentially transparent) front layer, afront electrode, an electro-optic layer and a backplane. In one form ofsuch a tile, the polymeric layer is textured to provide a plurality offacets, and the backplane is of the direct drive type having segments(pixel electrodes) aligned with the facets on the polymeric layer. Thebackplane may be in the form of a printed circuit board having thesegments mounted thereon. The electro-optic medium may be laminateddirectly on to the printed circuit board backplane.

Tiles of the present invention intended for use as ceiling tiles maydisplay a starry sky or similar pattern, and may be luminescent orphosphorescent. Alternatively, tiles may act as single pixels of a largedisplay; such a display may provide paths leading persons to a specificarea or destination, for example, the tiles may function as evacuationindicators in emergency situations, or the tiles may be used to formgraffiti walls.

Tiles of the present invention intended for use as ceiling tiles maydisplay a starry sky or similar pattern, and may be luminescent orphosphorescent. Alternatively, tiles may act as single pixels of a largedisplay; such a display may provide paths leading persons to a specificarea or destination, for example, the tiles may function as evacuationindicators in emergency situations, or the tiles may be used to formgraffiti walls.

In another aspect, this invention provides a variable color writableboard having a writable surface capable of being written on with amarker, and an electro-optic layer viewable through the writablesurface, the electro-optic layer being capable of displaying at leasttwo different colors, thereby enabling the appearance of the writableboard to be changed. Typically, such a variable color writable boardwill be provided with manually operable switching means to enable a userto select the color displayed by the electro-optic layer. For example,the board may be made white or black and/or any one of a selection ofcolors.

Writable boards are commercially available, for example, as whiteboards,blackboards, chalkboards, and marker boards. Prior commercial variantsof such boards are static such that the user cannot actively change abackground color electronically. The information written on the boardcan be erased using an eraser.

The term “marker” refers to a device that enables the user to write on awritable board. A marker dispenses an additive colorant, that is amixture of a subtractive colorant, which only absorbs light of certaincolors, and a light-scattering medium which scatters all wavelengths oflight. (A white marker for use on a blackboard may simply comprise alight-scattering medium without any colorant.) An “eraser” is a devicethat removes the layer of additive colorant deposited on to the writableboard by the marker. This removal is accomplished by scraping or wipingor transferring the additive colorant material on to the materialcomprising the eraser.

In another aspect, this invention provides a method of guiding a user toa selected one of a plurality of locations within an area, the methodcomprising:

-   -   providing, at a plurality of locations within the area, a        variable direction sign capable of displaying at least two        different direction indicators;    -   providing the user with a portable token containing information        identifying the selected location; and    -   bringing the portable token adjacent one of the variable        direction signs so that the one variable direction sign receives        at least part of the information identifying the selected        location, thereby causing the one variable direction to display        a direction indicator appropriate to guide the user to the        selected location.

In this method, information transfer between the token (which canconveniently be in the form of a credit card or hotel key sized device)and the variable direction indicators (signs) may be effected by directphysical contact, but the use of RFID or similar non-contact technologywill generally be preferred.

Finally, in another aspect, this invention provides a room dividercomprising: a plurality of color changing modules arranged in aplurality of rows and a plurality of columns, each module being arrangedto display at least two different colors, each module being pivotallyconnected to at least one module in a row above or below its own, andalso pivotally connected to at least one module in the same row; supportmeans arranged to support the modules above a floor or below a ceiling;and control means arranged to control the modules so that at least somemodules change color at times differing from those of other modules.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded isometric view of tile of the present inventionintended primarily for use as a wall tile.

FIG. 2 is a front plan view of the polymeric layer of the tile shown inFIG. 1.

FIG. 3 is an isometric view of the polymeric layer shown in FIG. 2 fromin front and to one side.

FIG. 4 is a schematic exploded three-quarter view of a writable board ofthe present invention viewed from in front, above and to one side.

FIG. 5 is an elevation of a room divider of the present invention.

FIG. 6 is a front plan view of a plurality of the tiles shown in FIG. 1in an installed condition.

DETAILED DESCRIPTION

As indicated above, the present invention provides a variety of deviceswhich make use of electro-optic displays. Although the various types ofdevices will mainly be described separately below, it will beappreciated that a single physical device may make use of more than oneaspect of the present invention; for example, a variable color wall ofthe present invention could incorporate a variable color marker board ofthe present invention and/or variable directional signs of the presentinvention.

Variable Color Tile

As already mentioned, in one aspect this invention provides a tilecomprising a light-transmissive (preferably essentially transparent)polymeric layer, a front electrode, an electro-optic layer and abackplane, the polymeric layer being textured to provide a plurality offacets, the tile further comprising a backplane of the direct drive typehaving segments (pixel electrodes) aligned with the facets on thepolymeric layer. The backplane may be in the form of a printed circuitboard having the segments mounted thereon. The electro-optic medium maybe laminated directly on to the printed circuit board backplane.

It is well known that color greatly affects the mood of persons in aroom, Blue and blue-white colors make rooms feel cooler and people morealert, where yellow and red colors tend to be warmer and create a morerelaxed feel. Places of public accommodation such as hotels, conferencecenters etc., are well aware of these effects of color and often arrangelighting such that its color can be varied depending upon the type ofevent for which a venue is being used. The tile of the present inventioncan take this mood shifting one step further by enabling the actualcolors walls, room dividers and other surfaces to be changed whendesired. In addition, the present tile can provide effects not readilyavailable from static paints or lighting; for example, the tiles candisplay ripples of color slowly moving across the wall, or aninteresting “twinkling” effects as the various facets undergo colorchanges. In some cases, for example night clubs, the colors of thetiles, or the rate of change of such colors, might be changeddynamically to match the mood of music being played. For example, in thecase of a large white/red display covering a substantial wall area (andsimilarly for other colors) a rapid shifting of red and white bandsacross the wall, with no use of intermediate colors, would convey aharsh, “edgy” atmosphere appropriate perhaps when rap music is beingplayed, whereas a much slower, more graduated flow of bands across thedisplay, with numerous intermediate shades being applied to ease thetransition of a particular pixel from white to red, would convey a muchmore relaxed atmosphere.

The manner in which the divisions between the facets of the front layermay be used to hide the divisions between backplane electrodes hasalready been discussed above. Careful arrangement of the divisionsbetween the facets may also be used for similar concealment purposes,for example to hide (or at least reduce the impact of) the gaps betweentile or between adjacent backplanes. Similarly, careful manipulation ofthe divisions between the facets may be used to conceal visible mountingfixture or apertures in the tiles.

A specific embodiment of the tile of the present invention will now bedescribed in more detail, though by way of illustration only, withreference to the accompanying drawings.

FIG. 1 is an exploded isometric view of a tile (intended primarily foruse as a wall tile, and generally designated 100) of the presentinvention. The tile 100 comprises a transparent molded front plate 102,which is discussed in more detail below with reference to FIGS. 2 and 3,and which has a flat rear surface in optical contact with the flat frontsurface of an electrophoretic display module 104. Methods forestablishing good optical contact between two planar surfaces such asthose on the front plate 102 and the display module 104, including theuse of optically clear adhesive, are well known to those skilled inoptics and are described, for example in the aforementioned U.S. Pat.No. 6,982,178 (see especially FIG. 20 and related description).

The internal details of the display module 104 are omitted from FIG. 1for clarity. However, the display module 104 may be substantially asdescribed in the aforementioned U.S. Pat. No. 6,982,178 and comprise, inorder from the front plate 102:

-   -   (a) a substantially transparent front (and typically        polymeric—although glass and other similar material may be used)        layer carrying a continuous substantially transparent front        electrode which extends across the entire display module 104;        the front layer and front electrode may be formed from a        commercially-available polyethylene terephthalate film;    -   (b) a layer of an encapsulated red/white electrophoretic medium;    -   (c) a layer of lamination adhesive; and    -   (d) a backplane bearing a plurality of discrete pixel electrodes        (discussed in more detail below).

The display module 104 is mounted on a component chassis 106 providedwith edge connectors 108 and an elongate aperture 110 which extendscompletely through the chassis 106. The chassis 106 is itself mounted ona mounting plate 112 provided at each corner with a cylindrical bore 114through which a screw 116 can be inserted to hold the mounting plate 112on a wall or other surface, or upon a wall rack comprising a series ofparallel strips. A printed circuit board 118, which acts as a displaycontroller for one or more tiles 100, is mounted in the center of themounting plate 112 and electrical connectors (not shown) extend from theboard 118 through the aperture 110 to each of the pixel electrodes ofthe display module 104 (so that the voltage applied to each pixelelectrode can be individually controlled), and to the edge connectors108. The board 118 may act as the controller for multiple tiles 100, oreven an entire wall display, or may simply control one tile, with theedge connectors 108 being used to pass timing signals to synchronize theswitching of the various tiles. The front plate 102, display module 104,chassis 106 and mounting plate 112 are each 12 inches (305 mm) square.

FIG. 2 is a front plan view of the front plate 102, with one facet 122highlighted, and FIG. 3 is an isometric view of the front plate 102 fromin front and to one side. The front plate 102 is, as already noted, 12inches (305 mm) square and approximately 3/16- 5/16 inch (approximately5-8 mm) thick. The front plate 102 is conveniently formed by injectionmolding of a transparent polymer, for example poly(methyl methacrylate).As best seen in FIG. 3, the front plate 102 has a flat rear surface 124,while as best seen in FIG. 2, its front surface 126 (FIG. 3) is dividedinto a large number of essentially polygonal facets, each having fromfour to seven vertices and each of which is tilted so that it is notexactly parallel to the plane of the display module 104. As indicated inFIG. 3, the facets are not exactly planar, but are slightly concaveoutwards, for reasons discussed above. The pixel electrodes are arrangedto that there is a single pixel electrode lying behind each facet of thefront plane 102.

As may be seen in FIG. 2, the arrangement of the facets on the frontplate 102 is carefully chosen so that when the tile 100 is surrounded byother tiles of the same pattern and in the same orientation, the linesdividing adjacent facets continue unbroken across the joins betweenadjacent tiles, so that two facets, one on each adjacent edge, form ineffect a compound facet, which is switched as a single unit, thusrendering the joins between tiles essentially invisible when the tilesare in operation undergoing color changes, and giving the impression ofa single continuous display. Specifically, the pairs of facets 128A/B,130A/B, 132A/B, 134A/B, 136A/B, 138A/B, 140A/B, 142A/B, 144A/B, 146A/Band 148A/B all form such compound facets, while the four corner facets150A/B/C/D together form a four-element compound facet, as illustratedin FIG. 6.

As already indicated, the tiles of the present invention may be drivenin a variety of ways. For example, a panel comprising a rectangulararray of tiles may start as a solid block of one color and thenindividual pixel electrodes are switched one at a time (except thatpairs or larger numbers of pixel electrodes associated with a compoundfacet are switched simultaneously) to the second color such that a bandof the second color progresses in an irregular manner across thedisplay. Eventually, the entire panel may be in the second color.Alternatively, after a substantial portion of the panel has been drivento the second color, a band of the first color may start to appear atthe edge from which the second color “emerged” so that alternating bandsof the two colors can follow each other across the panel. In eithercase, as previously noted the visual effect can be markedly altered bychanging the speed at which the bands progress and whether or notintermediate levels of color are used to spread out the transitionsbetween the two colors. Further possibilities include a “twinkling”effect by keeping most of the pixels at the same (background) color andrandomly switching a small proportion of pixels to the other color, thenback again, and a “firefly” effect, where again most of the pixels arekept at the background color but at various points first and secondadjacent pixels are switched to the second color, then a third pixel,adjacent to the second, is switched to the second color while the firstpixel is returned to the background color, so that the two-pixel“firefly” appears to execute a random dance around the panel. Otherdriving methods may of course be used, and additional complications inthe driving method are possible if more than two colors are available.

Variable Color Writable Board

As already mentioned, in one aspect the present invention provides awriteable board with an electro-optic color-changing background. Avariety of electro-optic materials, both emissive and reflective, may beused in such a board but reflective media are generally preferred. Forexample, organic light emitting diodes (OLEDs), encapsulated liquidcrystals, for example polymer-dispersed liquid crystals, andelectrochromic media may all be used in the present invention, however,the preferred embodiment uses an encapsulated, polymer-dispersed ormicrocell electrophoretic imaging medium. In the variable colorwriteable board of the present invention, the reflective or absorptivelayer in a conventional whiteboard or blackboard is replaced by a layerof electro-optic medium, and a marking medium comprised of an additivecolorant (a subtractive colorant and a highly scattering medium) isapplied to the exposed surface of the display.

By creating a writing board which the user can make white or colored,users are given the flexibility to choose properties previously onlyavailable in separate boards. A variable color writeable board can beused as a blackboard (chalkboard) when the higher contrast and hapticfeedback function of a blackboard is desired, or used as a whiteboardwhere users want to display information via interactive projection(i.e., to use the board as a projection screen) or seek to increase thevividness of colored writing.

A protective layer (a layer of light-transmissive and preferablytransparent material) may be placed between the electro-optic layer andthe viewing/writing surface to protect the electro-optic layer frommechanical or other damage. The protective layer may be the writablelayer itself or may be a separate layer disposed between theelectro-optic layer and the writable layer. The viewing/writing surfaceof the display may be surface treated (roughened) to allow the additivecolorant to deposit easily from the marker. Alternatively, anelectro-optic film similar to the front plane laminate described in theaforementioned U.S. Pat. No. 6,982,178 may be used in the presentinvention in conjunction with a suitable backplane and with a protectivelayer placed between the electro-optic film and the writing surface toprotect it from damage and/or scratching.

An “optical coupling layer” (a layer of material chosen to reduce lightlosses) may be placed between an electro-optic layer and a protectivelayer, or, if an electro-optic film is employed, between theelectro-optic film and a protective layer to reduce the light lossesbetween the two surfaces.

A mechanical support structure (“device frame”) may be used to hold thewritable board assembly together and to anchor it to any architecturalsurface (wall, door, etc. . . . ) of the user's choice. Displays mayalso be attached to a structure via lamination, frame holders, screws(preferably electrically non-conductive screws) or other known means.

FIG. 4 is a schematic exploded of one writable board of the presentinvention showing the multiple layers of a variable color writeableboard. A first layer (401), an electro-optic film, is placed adjacentthe rear surface of the display. The electro-optic film may be drivenvia a common front electrode and a backplane that may be in form of asingle rear electrode, a segmented (direct drive) backplane (in whicheach segment is provided with an individual conductor to control thevoltage of the segment) or an active or passive matrix backplane. (Notall types of electro-optic medium are usable with all types ofbackplane.) The electro-optic layer contains an encapsulatedelectrophoretic medium capable of achieving electrically tunable opticalstates of varying color and reflectivity. The construction of theelectro-optic layer and its lamination to the desired backplane may beaccomplished via techniques known in the art. The layer (401) also has abus (409) whereby electrical connections to the circuitry needed todrive the display can be made.

A second layer (402) termed the optical coupling layer, which iscomprised of an optical coupling adhesive or optically clear adhesive,is disposed above the first layer (401). The layer (402) may be attachedto the first layer (401) using techniques known in the art. The purposeof the second layer is to reduce the optical losses between the firstand third layers.

A third layer (403), also called the protective layer, is disposed abovethe second layer. The purpose of the third layer is to mechanicallyshield the layers below it. Materials used in this layer are well knownin the art. Materials like glass, acrylic, and polycarbonate are usedextensively in the marker board/chalkboard industry. The surface of thethird layer is treated so as to receive the additive colorant and enableits removal with an eraser. The third layer may also be patterned via aprinting process or decal on the back to create decorative, aesthetic orfunctional accents.

A fourth layer (404), also known as the device frame, is placed aroundthe first, second and third layers. The purpose of the fourth layer isto provide a means of mechanically supporting the device and anchoringit to an architectural surface. Numerous ways of constructing such aframe are known in the art. The layer may also have specific shape andform to permit decorative, aesthetic or functional enhancements. Thislayer also has a place to house the electrical circuitry (408) needed todrive the electro-optic layer; alternatively, instead of accommodatingthe drive circuitry itself, this layer may accommodate a wiredelectrical connector or a wireless connection device (for example, aWifi or Bluetooth module) for relaying data to or from remote drivecircuitry. The frame may house a digitization device (known in the art)needed to capture the marker position and an interactive projector fordisplaying information on the board. A marker (405) is comprised of adispenser of additive colorant which can transfer on to the third layerand produce writing of the user's choice. A number of commerciallyavailable technologies can fulfil this role. For example, chalkmanufactured by “Chalk Ink” etc. may be used for this purpose. Themarker may also be part of an electronic digitization solution. Suchsolutions are known in the art. An eraser (406) is comprised of a spongymaterial. This device can be used to remove the additive colorantdispensed by the marker from the third layer. Many means of achievingthis are known in the art.

The board shown in FIG. 4 may be assembled by placing the desiredaesthetic pattern or decorative decal on the back of the third layer(403), adhering the first (401), second (402) and third (403) layerstogether using any means known in the art, electrically connecting thefirst layer (401) to the drive electronics and housing the electronicsin the fourth layer (404).

Alternatively, a fifth layer (407) may be added behind the first layer(401). The purpose of this layer is to add mechanical support oradditional properties as desired. For example, the fifth layer (407) maybe a steel layer placed behind the first layer to create a writableboard that also has magnetic properties to magnetically attachaccessories associated with magnetic boards known in the art. In anotheralternative, the choice of materials in the first (401), second (402),third (403), fourth (404) and fifth (407) layers may be such that theentire device is flexible and/or can be molded on to a curved surface.

As already mentioned, the third layer may also be patterned via aprinting process or decal on the back to create decorative, aesthetic orfunctional accents. For example, a portion of the third layer may beused to display a glyph (such as name, abbreviation, trademark, logo,seal or heraldic achievement) of the institution in which the board islocated). However, greater flexibility may be achieved by using aportion of the electro-optic layer itself (for example, one corner ofthe display or a strip along one edge of the display) to display thedesired glyph. Known overlay techniques familiar from televisionbroadcasts may be applied to the drive circuitry of the electro-opticlayer such that a portion of the display is reserved for the glyph anddoes not change with the rest of the display. Alternatively, the drivecircuitry may be arranged so that the pixels comprising the glyph remainconstant regardless of the colors changes applied to the surroundingpixels, or are always in a color state contrasting with the surroundingpixels regardless of the color changes applied to those surroundingpixels. Provision of an “electronic glyph” in any of these ways has theimportant advantage that the glyph can be changed to accommodatedifferent users; for example, a board at a conference center coulddisplay a glyph associated with the specific conference or sponsor ofthe event taking place at any time.

As discussed in more detail below, electro-optic media may usefully beemployed to provide color varying permanent or temporary walls andsimilar structures (such as room dividers and screens), ceilings, floorsand surfaces of furniture and other building fittings. Variable colorwritable boards of the present invention offer the possibility ofproviding a writable board which essentially vanishes when not in use.If the writable board is mounted essentially flush with the surroundingwall, screen or other surface (for example, the surface of a variabledirectional sign or of a file cabinet), and appropriate drive circuitryand switch are provided), the writable board, when not in use, canundergo the same color changes as the surrounding surface and will thusappear to be a part of that surface. When the writable board is requiredto function as such, the switch is thrown and the writable board thenfunctions independently of the surrounding surface.

Other Architectural and Furniture Applications

The light weight and low power consumption of electrophoretic andsimilar electro-optic displays render them very suitable for use in roomdividers, especially room dividers which are suspended from above. Suchroom dividers may have the form of a plurality of tiles connected toeach other by connectors which permit relative movement between thetiles. Such multi-tile room dividers allow for visually interestingconfigurations; for example, even though the room divider is suspendedat intervals from a linear rail, the divider may assume a serpentine orsimilar curved configuration.

Electro-optic displays may be especially useful in sculptures, includingsuspended sculptures and mobiles. The provision of color changingtechnology can greatly enhance the esthetic experience of sculptures,especially when combined with the physical movement of mobilesculptures.

Furniture surfaces which may be enhanced by the present inventioninclude table tops, chairs, countertops, door and cabinets. Anelectro-optic medium may be laminated or otherwise attached by knownmethods to an exposed surface of the furniture or may be embedded withinthe article, for example a door, table or cabinet, by known methods ofplacing the electro-optic medium and associated electrodes within acavity, filling the cavity with a polymerizable medium and thensubjecting the polymerizable medium to conditions, such as heat orexposure to radiation, which could the polymerizable medium topolymerize, thereby embedding the electro-optic medium and electrodeswith a light-transmissive polymer. Alternatively, the electro-opticmedium and electrodes may be laminated between two sheets of glass orother light-transmissive material. As with writeable boards,architectural surfaces may usefully incorporate an optical couplinglayer to reduce light losses between the two surfaces.

Incorporating electro-optic displays into furniture in accordance withthe present invention can accomplish far more than providing improvedesthetic appearances; the electro-optic displays can enhance thefunctions of the furniture. For example, provision of an electro-opticdisplay in a coffee table not only enables interesting effects usingcolor changes in the table but can also enable the table to function asa games table; the upper surface of the table could display games board,for example chess/checkers, backgammon or cribbage. Note that such atable, especially if provided with touch sensing capability, couldprovide more than the board for a game; the table could also display thegame pieces and permit them to be moved. A restaurant table coulddisplay the menu and wine list. An arm of a chair could be provided witha display an infra-emitter to act as a remote controller for atelevision and/or other electronic device.

Another use for which electro-optic media are well-adapted isinformation sharing. Many public spaces, such as streets, plaza, parks,university campuses, conference centers, places of public assembly etc.,are replete with directional and other signs, for which there is anobvious need in any place frequently by people not familiar with thelocation. Many such signs need to be of substantial size so as to bereadily readable from a significant distance. However, the presence ofmany large signs gives rise to “visual clutter” which many people findobjectionable. Furthermore, many signs need to convey differentinformation to different groups of users. For example, on a universitycampus where most students are familiar with the general layout of thecampus, it may be sufficient for a sign to announce that a particularmeeting is taking in (say) “Smith's Theater” since students mayreasonably be assumed to know the location of Smith's Theater. However,when parents descend on the campus for Parents' Weekend, they will notknow the location of Smith's Theater and the sign really needs todisplay a map of the campus with the location of Smith's Theaterhighlighted.

Signs using electro-optic media in accordance with the present inventioncan meet many of the problems with conventional fixed directional andother signs. When not in immediate use, the signs can be renderedinconspicuous by being set (mostly) to a color which blends into thebackground, leaving just a small area, marked perhaps with a questionmark, which a user presses to activate the sign. The sign could thendisplay a menu, which could be multi-tiered, asking the user to indicatewhat information is desired. Some pages of displayed information couldinclude prompts asking if further information is desired; for example, alist of that day's meetings and corresponding rooms could include anoption for “Is campus map desired?” The menu could also ask the class ofuser (for example, freshman student, upper classman or parent) and varythe displayed pages depending upon this class.

The ability to customize the displayed page depending upon the user canbe enhanced if the display is provided with some sensor capable ofreceiving information from a portable token (for example, a boardingpass or hotel room “key”) carried by a user. Such information exchangebetween a sign and a portable token can readily be carried out by RFID,Bluetooth or other known technologies. For example, a guest in a hotelor a patient in a hospital can be issued with a card customized to theroom to be occupied or visited. As the guest/patient traverses thecorridors of the hotel/hospital, he places the card adjacent a signfound at each corridor intersection, whereupon the sign changes toindicate the direction in which he should proceed.

The effect of color changes on users of enclosed spaces has beendiscussed above. However, color changes on architectural surfaces mayserve more than esthetic purposes. With fixed color walls and doors, itis often necessary to deploy numerous signs, and possibly to mark offareas with safety tape, when an area of a building has to be closed tothe public or to other than a selected group of people (for example,construction workers). Storing and deploying the necessary signs andtape is a labor-intensive process. If both color changing walls anddoors are provided, an area of the building can be closed by (say)setting the walls and doors to a red color and displaying a “Danger—Nounauthorized persons” or similar warning on the doors.

As previously noted, the light weight and low power consumption ofelectrophoretic and similar electro-optic displays render them verysuitable for use in room dividers, especially suspended room dividers;such dividers may have the form of a plurality of tiles connected toeach other by connectors which permit relative movement between thetiles. FIG. 5 illustrates such a divider, generally designated 500. Theroom divider 500 is suspended from a linear rail (not shown) by aplurality of supports 502, each of which can be in the form of a conduithousing data and power cables. (Alternatively, data communication to thedivider may be by wireless transmission and power may be generatedinternally by photovoltaic cells.) The divider consists of a largenumber of flat, hexagonal modules 504 each of which is switchablebetween yellow and white (and is capable of displaying intermediateshades). Although not easily seen in FIG. 5, each hexagonal module 504is supported from above by two vertical connectors passing through themidpoints of its two upper edges, these vertical connectors permittingthe two modules which they join to rotate relative to one another. Twosimilar vertical connectors enable each module to support the modulebelow. Each module 504 is also pivotably connected via its side edges tothe modules on either side. The vertical connectors permit data to passbetween the modules which they link. Control of the various modules by acontroller (not shown) may be by master/slave techniques or by cascadingtechniques. The controller may be preloaded with sequences that may beselected by a user, or may be actively updated to change/reload theprogramming.

As will be seen in FIG. 5, although the supports hang from a linearrail, the flexible connections between the various modules 504 permitthe overall configuration of the room divider 500 to deviate from thevertical plane containing the rail. The divider 500 may assume aserpentine configuration as shown in FIG. 5, or a different curvedconfiguration, with the change of configuration typically being effectedmanually.

It will be apparent to those skilled in the art that numerous changesand modifications can be made in the specific embodiments of theinvention described above without departing from the scope of theinvention. Accordingly, the whole of the foregoing description is to beinterpreted in an illustrative and not in a limitative sense.

The invention claimed is:
 1. A plurality of tiles, each tile comprising,in order: a light-transmissive front layer; at least one frontelectrode; an electro-optic layer capable of changing the color of thetile; and a plurality of rear electrodes, wherein an exposed surface ofthe front layer includes a plurality of facets along at least one edgeof each tile having a plurality of inclinations to a plane of theexposed surface of the tile and when the plurality of tiles are in aninstalled condition, the plurality of facets along the at least one edgeof adjacent tiles form a plurality of irregular polygonal shapedcompound facets switching as a single unit at a joint between theadjacent tiles, at least some lines dividing adjacent facets continueunbroken across the joints between adjacent tiles and obscure the joint.2. The plurality of tiles according to claim 1 wherein the majority ofthe facets do not lie parallel to the plane of the electro-optic layer.3. The plurality of tiles according to claim 1 wherein at least one ofthe facets is concave outwards.
 4. The plurality of tiles according toclaim 1 wherein the irregular polygonal shaped compound facets have fromfour to eight vertices.
 5. The plurality of tiles according to claim 1wherein the backplane has the form of a plurality of discrete electrodeseach of which is substantially aligned with one of the facets of thefront layer.
 6. The plurality of tiles according to claim 1 wherein thebackplane is an active matrix backplane having a matrix of electrodesarranged in a plurality of rows and a plurality of columns.